1. Field of the Invention
The present invention is generally related to liquid natural gas (LNG) processing systems, and, more particularly, to a floating LNG regasification facility with an LNG storage vessel.
2. Description of the Related Art
Natural gas is captured from subterranean structures via natural gas wells. The natural gas is then processed to convert it from a gaseous state to a liquid state—liquefied natural gas (LNG). LNG is typically transported as a liquid via specialized LNG carrier vessels. A floating LNG terminal is provided for offloading the LNG carrier vessel in the sea. The floating LNG terminal typically comprises a regasification vessel that is used to regasify the LNG, i.e., to convert the liquid gas to its gaseous form. The gas is then transported to various onshore facilities via undersea gas pipelines.
The marine operations involved in safely berthing an LNG carrier to another floating vessel in the open sea are known by the offshore industry to be a dangerous, high risk endeavor. It is generally understood that sea-going tug boats cannot safely operate to push against the side of an LNG carrier under high sea conditions, e.g., seas having a significant wave height (Hs) greater than about 1-1.5 meters. Generally during berthing operations, the LNG carrier is positioned such that the longitudinal axis of the LNG carrier lies approximately parallel, more or less, to the direction of the wind and waves. Accordingly, in operation, the sea-going tug boats that push on the sides of the LNG vessel are positioned more broadside to the wind and waves and therefore suffer severe rolling motion while they attempt to push an LNG carrier toward its berth adjacent another floating vessel. To the extent that the LNG carrier and the other floating vessel to which it will be berthed have traditional hull configurations, the problems associated with berthing may be more difficult as both vessels may tend to roll with an increasing relative magnitude as they approach one another.
In many situations, the regasification process is a limiting factor as it relates to how fast the LNG can be offloaded from an LNG carrier vessel. For example, an LNG carrier vessel may be temporarily moored to the regasification vessel for three days to fully offload and regasify the LNG on the LNG carrier vessel. The specialized LNG carrier vessels are very expensive to operate. The time spent in completely offloading a loaded LNG carrier vessel is very expensive. Moreover, the longer the loaded LNG carrier vessel remains positioned beside the regasification vessel and connected for offloading LNG, the greater the possibility of mishaps or accidents occurring. Additionally, consumers that purchase the gasified LNG typically like to have the purchased volume supplied to them in a continuous fashion. For example, some customers do not like to receive one-half of the purchased quantity on day 1 and have to wait until, for example, day 5 to receive the remainder of the purchased product. With existing offshore LNG terminals, depending upon the timing of the customer's overall product demand and the arrival of the seagoing LNG carrier vessels, it may not be possible to supply the purchased product in a continuous fashion.
The present invention is directed to various devices and methods for solving, or at least reducing the effects of, some or all of the aforementioned problems.